The present invention relates to catalytic polymerization of alpha-olefins, and more particularly, to a method for catalytic polymerization of alpha-olefin monomers using an ultra-high activity non-metallocene pre-catalyst featuring an amine bis(phenolate) ligand-metal chelate.
Currently, there is significant interest relating to methods and systems of catalytic polymerization of alpha-olefin monomers based on a xe2x80x98pre-catalystxe2x80x99 featuring a metal bound to one or more spectator ligands, where the pre-catalyst may be soluble in a liquid phase solvent, or is adsorbed on a solid surface, and where alpha-olefin monomer reactant may be liquid or gas phase. In such methods and systems, typically, the pre-catalyst is activated by at least one xe2x80x98co-catalystxe2x80x99, where the combination of the activated pre-catalyst and the at least one co-catalyst functions as a single chemical entity, or complex xe2x80x98catalystxe2x80x99, for polymerization of the alpha-olefin monomer. The field of catalytic polymerization of alpha-olefin monomers is of significant industrial importance, as more than 50 million tons of poly(alpha-olefin) products, such as polyetheylenes and polypropylenes, are produced each year, involving metal based catalytic processes and systems.
Hereinafter, the term xe2x80x98pre-catalystxe2x80x99 refers to a chemical entity, in general, and to a chemical compound, in particular, which, when activated by at least one xe2x80x98co-catalystxe2x80x99, becomes part of a xe2x80x98catalystxe2x80x99 functional for catalytic polymerization of an alpha-olefin monomer, under proper polymerization reaction conditions. In general, without the presence of at least one co-catalyst, a pre-catalyst is ineffective for catalytic polymerization of an alpha-olefin monomer, and consequently exhibits essentially no catalytic activity for polymerization of an alpha-olefin monomer. Here, when referring to catalytic activity during a polymerization reaction, reference is with respect to the catalytic activity of a pre-catalyst, and it is to be understood that the pre-catalyst functions in concert with at least one co-catalyst for effecting catalytic polymerization of an alpha-olefin monomer. It is noted, however, that there are rare exceptions of a particular pre-catalyst functioning without first being activated by a co-catalyst, for effecting catalytic polymerization of an alpha-olefin monomer. Thus, the present invention focuses on a new and novel pre-catalyst compared to pre-catalysts currently used for catalytic polymerization of alpha-olefin monomers.
Currently, one of the major goals in this field is to produce a variety of new types of poly(alpha-olefin) products, for example, polymers made from alpha-olefin monomers featuring more than two carbon atoms, having well defined bulk or global physicochemical properties, such as mechanical strength, elasticity, melting point, and chemical resistance, applicable for manufacturing a diversity of end products. This may be achieved by controlling the polymer tacticity and polymerizing different types of alpha-olefin monomers, in order to produce a variety of homo-polymers and co-polymers, with varying degrees of monomer incorporation.
Typically, degree of monomer incorporation strongly depends upon catalyst activity for polymerization of a given alpha-olefin monomer. Recently, Britovsek, G. J. P., et al., in xe2x80x9cThe Search For New-Generation Olefin Polymerization Catalysts: Life Beyond Metallocenesxe2x80x9d, Angew. Chem. Int. Ed. Engl. 38, 428-447, 1999, provided a practical quantitative ranking of catalytic activity, with respect to weight of a pre-catalyst, (grams polymer produced)/(mmole-pre-cat. hr), for ethylene polymerization, under one bar pressure, as follows: very low less than 1, low 1-10, moderate 10-100, high 100-1000, very high greater than 1000. Their ranking is derived from data of catalytic polymerization of ethylene, which is the easiest alpha-olefin monomer to polymerize. Catalytic activity for polymerization of other larger alpha-olefin monomers, such as 1-hexene and 1-octene, is usually at least one order of magnitude less. Thus, a pre-catalyst for polymerization of 1-hexene, for example, may be considered exhibiting high, and very high, activity in the range of about 10-100, and 100-1000, grams/(mmole-pre-cat. hr), respectively.
Bulk or global physicochemical properties of polymers are directly related to, and are controllable by, molecular or local physicochemical characteristics of the polymer units making up the bulk polymer. Two notable molecular physicochemical characteristics are polymer molecular weight and polymer molecular weight distribution.
Polymer molecular weight and polymer molecular weight distribution are highly relevant with respect to producing different types of polymers. For example, ultra-high molecular weight polyethylene (UHMWPE), having an average molecular weight above 3,000,000, has the highest abrasion resistance of thermoplastics and a low coefficient of friction. Unlike synthesis of small molecules, however, polymerization reactions involve random events characterized by formation of polymer chains having a range of molecular weights, rather than a single molecular weight. Typically, polymers are better defined and characterized in relation to narrow molecular weight ranges.
The accepted parameter for defining polymer molecular weight distribution is the polydispersity index (PDI), which is the weight average molecular weight, Mw, divided by the number average molecular weight, Mn, or, Mw/Mn. Depending upon the actual application, ideally, a catalytic polymerization system features xe2x80x98livingxe2x80x99 polymerization in which the rate of initiation is higher than the rate of propagation, involving a single catalytic active site, and the rate of termination reactions is negligible relative to propagation, thus, leading to a PDI of close to 1. This has been achieved in very few systems for catalytic polymerization of alpha-olefin monomers. A PDI of 2.0, signifying xe2x80x98non-livingxe2x80x99 polymerization, is often found in metallocene catalytic systems, also involving a single catalytic active site. Classical heterogeneous Ziegler-Natta catalytic systems usually lead to a broader range of molecular weights with a PDI of about 5. One current challenge is to design alpha-olefin polymerization pre-catalysts, and catalytic systems including such pre-catalysts, leading to poly(alpha-olefin) products with low values of PDI.
Metallocene pre-catalysts, featuring a metal complex including a metal atom, for example from Group IV transition elements such as titanium, zirconium, and hafnium, bound to two ligands from the well known cyclopentadienyl (Cp) family of ligands such as pentamethylcyclopentadienyl, indenyl, or fluorenyl, were introduced during the last two decades for the purpose of catalytic polymerization of alpha-olefin monomers. The most common type of metallocene pre-catalyst is a neutral complex including a metal in oxidation state of +4, bound to two anionic ligands in addition to two standard Cp ligands, for example, bis(cyclopentadienyl)titanium dichloride, also known as titanocene dichloride. A particular group of metallocene pre-catalysts is known as ansa-metallocene complexes, in which the two Cp type ligands are covalently bonded to each other. A related group of complexes is xe2x80x98constrained geometryxe2x80x99 pre-catalysts, featuring a metal bound to both a single Cp type ligand and a second anionic group, where the Cp ligand and second anionic group are covalently bonded to each other.
Using metallocene and metallocene type pre-catalysts in catalytic processes and systems for polymerization of alpha-olefin monomers affords better control of molecular weight and narrower molecular weight distribution, associated with lower values of PDI, relative to the classical Ziegler-Natta family of pre-catalysts such as titanium trichloride using a trialkyl-aluminum co-catalyst. Metallocene and metallocene type pre-catalysts, processes, and systems are well known and taught about in the art. These pre-catalysts, processes and systems are, however, limited in many respects relating to the above discussion.
Foremost, with respect to catalytic activity, metallocene type pre-catalysts typically exhibit relatively moderate activity for polymerizing a small variety of alpha-olefin monomers. With respect to poly(alpha-olefin) product types and variety, alpha-olefin monomers polymerized by metallocene pre-catalysts are mostly short chain ethylene and propylene, which are already well taught about. Metallocene pre-catalysts are limited in terms of availability and versatility. Metallocene type pre-catalysts are relatively difficult to synthesize, a fact which limits the possibility of developing new varieties of metallocene type alpha-olefin polymerization pre-catalysts.
Due to continued searching for new poly(alpha-olefin) products exhibiting selected well defined bulk physicochemical properties and molecular physicochemical characteristics, combined with the above limitations associated with metallocene pre-catalysts, there is growing interest in developing non-metallocene alpha-olefin polymerization pre-catalysts, and related catalytic processes, and systems. The main emphasis is on obtaining new alpha-olefin polymerization pre-catalysts which are readily available, exhibit relatively high stability, and can be used for improving control over industrially important polymer parameters such as molecular weight, molecular weight distribution, product type, and variety.
The first step towards development of non-metallocene pre-catalysts was taken by the introduction of a xe2x80x98half sandwichxe2x80x99 pre-catalyst, featuring a complex including a Cp type ligand bridging to a heteroatom donor. An example of such a pre-catalyst is a phenolate constrained geometry polymerization pre-catalyst disclosed in U.S. Pat. No. 5,856,258. The pre-catalyst described therein shows relatively high activity of about 1,300 grams/(mmole-pre-cat. hr) for polymerization of alpha-olefin monomers, however monomers polymerized are limited to ethylene, propylene, and styrene.
A non-metallocene alpha-olefin polymerization catalytic system is disclosed in U.S. Pat. No. 5,852,146, and features a bis(hydroxy aromatic nitrogen ligand) transition metal pre-catalyst, functioning with an activating methylaminoxane (MAO) co-catalyst. Relatively high catalytic activity of about 4,000 grams/(mmole-pre-cat. hr) is reported for polymerization of ethylene only. Moreover, MAO is needed in large quantities as co-catalyst, which, in general poses notable limitations relating to cost and containment. MAO used in large quantities is costly, and needs to be properly disposed of with regard to environmental considerations.
Living polymerization of 1-hexene is recently described by Schrock, R. R., in J. Am. Chem. Soc. 119, 3830, 1997, and is disclosed in U.S. Pat. No. 5,889,128. One of the non-metallocene pre-catalyst compositions described therein comprises a dimethyl complex in which the metal atom is chelated to a tridentate spectator ligand, which is activated by a non-MAO boron salt co-catalyst. Catalytic activity under the conditions described was considered high, of about 200 grams/(mmole-pre-cat. hr), and the molecular weight of the obtained poly(1-hexene) product is moderate, of about 50,000 grams/mole.
Living polymerization of 1-hexene is also described by McConville, D. H., in J Am. Chem. Soc. 118, 10008, 1996. They describe a moderately active non-metallocene polymerization pre-catalyst, exhibiting activity of about 40 g/(mmole-pre-cat. hr), involving activation of a pre-catalyst featuring a dimethyl metal complex of a bis(amide) ligand, with a non-MAO boron Lewis acid as co-catalyst under room temperature, for producing a moderate molecular weight polymer, of molecular weight of 40,000 grams/mole. The same pre-catalyst, but functioning with MAO as co-catalyst in large excess, under the same reaction conditions, yields significantly higher activity, as reported by McConville, D. H., in Macromolecules V. 29, 5241, 1996. Again, limitations associated with using MAO as co-catalyst are present.
Another active non-metallocene living 1-hexene polymerization pre-catalyst functioning with a non-MAO co-catalyst, is reported by Kim, K., in Organometallics 17, 3161, 1998. The described catalyst system exhibits activity of about 400 grams/(mmole-pre-cat. hr).
A non-metallocene non-living 1-hexene polymerization pre-catalyst is disclosed in U.S. Pat. No. 5,807,801. The pre-catalyst exhibits high activity, of on the order of 106 g/(mmole-pre-cat. hr), when the pre-catalyst is, again, activated with MAO as co-catalyst, for the polymerization process taking place at 50xc2x0 C.
A non-metallocene bis(phenolate) pre-catalyst is reported by Schaverien, C. J., in J. Am. Chem. Soc. 117, 3008, 1995. The pre-catalyst described exhibits limited activity, of about 10 g/(mmole-pre-cat. hr), for tactic polymerization of 1-hexene, yielding high molecular weight isotactic poly(1-hexene).
A potentially important industrial application of living polymerization of alpha-olefin monomers is the synthesis of block copolymers. This requires either total or nearly total consumption of the first monomer to produce a narrow PDI fragment before addition of the second monomer, upon which the polymerization process should resume. These requirements are extremely difficult to attain, and therefore it is no surprise that despite the intensive efforts invested in the field of alpha-olefin polymerization, very few systems that induce living polymerization of alpha-olefin monomers are known to be applicable for producing block co-polymers. Moreover, all such prior art polymerization systems operate below room temperature (25xc2x0 C.).
In view of the above discussed limitations for polymerization of alpha-olefins, to one of ordinary skill in the art, there is thus a need for, and it would be highly advantageous to have a method for catalytic polymerization of alpha-olefin monomers using an ultra-high activity non-metallocene pre-catalyst, where the pre-catalyst is not limited to activation by large quantities of a co-catalyst such as MAO, is characterized by high stability, and is readily obtained or synthesized. There is also a need for such a method of polymerization which is capable of producing different types and varieties of poly(alpha-olefin) products having high molecular weight, and low molecular weight distribution, of being performed at and above room temperature, of exhibiting living polymerization at and above room temperature, and, of producing block copolymers. Moreover, there is a need for such a method using the pre-catalyst for producing alpha-olefin polymers other than polyethylenes and polypropylenes, having industrially applicable properties and characteristics.
The present invention relates to a method for catalytic polymerization of alpha-olefin monomers using an ultra-high activity non-metallocene pre-catalyst featuring an amine bis(phenolate) ligand-metal chelate.
Thus, according to the present invention, there is provided a method for catalytic polymerization of an alpha-olefin monomer comprising the steps of: (a) providing a particular form of an amine bis(phenolate) pre-catalyst having a general structure selected from the group consisting of: 
wherein: a solid line represents a covalent bond; a dashed line represents a bond having a varying degree of covalency and a varying degree of coordination; M is a metal atom covalently bonded to each O atom and bonded with varying degrees of covalency and coordination to the N atom; X1 and X2 are each a univalent anionic ligand covalently bonded to the metal atom; X3 is a single divalent anionic ligand covalently bonded to the metal atom; R1 through R4 are each a univalent radical covalently bonded to first (C6) aromatic group; R5 through R8 are each a univalent radical covalently bonded to second (C6) aromatic group; and (RnYxe2x80x94T) is an optional group selected from the group consisting of a non-donor group covalently bonded to the N atom, wherein the non-donor group, the T is a covalent bridging group between the N atom and the Y, the Y is a group covalently bonded to the T, and, each of at least one Rn is selected from the group consisting of a saturated substituent covalently bonded to the Y, an unsaturated substituent covalently bonded to the Y, and a univalent radical covalently bonded to the Y, and a donor group covalently bonded to the N atom, wherein the donor group, the T is a covalent bridging group between the N atom and the Y, the Y is a heteroatom covalently bonded to the T and bonded with varying degrees of covalency and coordination to the metal atom, and, optional Rn substituents are selected from the group consisting of at least one saturated substituent covalently bonded to the Y, and at least one unsaturated substituent covalently bonded to the Y; (b) preparing a first chemical entity featuring the particular form of the amine bis(phenolate) pre-catalyst of step (a); (c) providing a co-catalyst suitable for activating the particular form of the amine bis(phenolate) pre-catalyst; (d) preparing a second chemical entity featuring the provided co-catalyst of step (c); (e) forming a catalytic polymerization reaction by mixing (i) the first chemical entity featuring the particular form of the amine bis(phenolate) pre-catalyst, with (ii) the second chemical entity of the provided co-catalyst, with (iii) the alpha-olefin monomer to be catalytically polymerized, whereby the co-catalyst activates the pre-catalyst, whereby combination of the pre-catalyst and the co-catalyst becomes a catalyst for effecting the catalytic polymerization of the alpha-olefin monomer and for producing at least one poly(alpha-olefin) product; (f) allowing the catalytic polymerization reaction to progress; (g) terminating the catalytic polymerization reaction; and (h) isolating the at least one poly(alpha-olefin) product formed by the catalytic polymerization reaction.
According to another aspect of the present invention, there is provided a method for catalytic polymerization of an alpha-olefin monomer comprising the steps of: (a) providing a particular form of an amine bis(phenolate) catalyst having a general structure selected from the group consisting of: 
wherein: a solid line represents a covalent bond; a dashed line represents a bond having a varying degree of covalency and a varying degree of coordination; M is a metal atom covalently bonded to each O atom and bonded with varying degrees of covalency and coordination to the N atom; X1 and X2 are each a univalent anionic ligand covalently bonded to the metal atom; X3 is a single divalent anionic ligand covalently bonded to the metal atom; R1 through R4 are each a univalent radical covalently bonded to first (C6) aromatic group; R5 through R8 are each a univalent radical covalently bonded to second (C6) aromatic group; and (RnYxe2x80x94T) is an optional group selected from the group consisting of a non-donor group covalently bonded to the N atom, wherein the non-donor group, the T is a covalent bridging group between the N atom and the Y, the Y is a group covalently bonded to the T, and, each of at least one Rn is selected from the group consisting of a saturated substituent covalently bonded to the Y, an unsaturated substituent covalently bonded to the Y, and a univalent radical covalently bonded to the Y, and a donor group covalently bonded to the N atom, wherein the donor group, the T is a covalent bridging group between the N atom and the Y, the Y is a heteroatom covalently bonded to the T and bonded with varying degrees of covalency and coordination to the metal atom, and, optional Rn substituents are selected from the group consisting of at least one saturated substituent covalently bonded to the Y, and at least one unsaturated substituent covalently bonded to the Y; (b) preparing a first chemical entity featuring the particular form of the amine bis(phenolate) catalyst of step (a); (c) forming a catalytic polymerization reaction by mixing (i) the first chemical entity featuring the particular form of the amine bis(phenolate) catalyst, with (ii) the alpha-olefin monomer to be catalytically polymerized, whereby the amine bis(phenolate) catalyst effects the catalytic polymerization of the alpha-olefin monomer for producing at least one poly(alpha-olefin) product; (d) allowing the catalytic polymerization reaction to progress; (e) terminating the catalytic polymerization reaction; and (f) isolating the at least one poly(alpha-olefin) product formed by the catalytic polymerization reaction.
According to another aspect of the present invention, there is provided a method for living catalytic polymerization of an alpha-olefin monomer comprising the steps of: (a) providing a particular form of an amine bis(phenolate) pre-catalyst having a general structure selected from the group consisting of: 
wherein: a solid line represents a covalent bond; a dashed line represents a bond having a varying degree of covalency and a varying degree of coordination; M is a metal atom covalently bonded to each O atom and bonded with varying degrees of covalency and coordination to the N atom; X1 and X2 are each a univalent anionic ligand covalently bonded to the metal atom; X3 is a single divalent anionic ligand covalently bonded to the metal atom; R1 through R4 are each a univalent radical covalently bonded to first (C6) aromatic group; R5 through R8 are each a univalent radical covalently bonded to second (C6) aromatic group; and (RnYxe2x80x94T) is an optional group selected from the group consisting of a non-donor group covalently bonded to the N atom, wherein the non-donor group, the T is a covalent bridging group between the N atom and the Y, the Y is a group covalently bonded to the T, and, each of at least one Rn is selected from the group consisting of a saturated substituent covalently bonded to the Y, an unsaturated substituent covalently bonded to the Y, and a univalent radical covalently bonded to the Y, and a donor group covalently bonded to the N atom, wherein the donor group, the T is a covalent bridging group between the N atom and the Y, the Y is a heteroatom covalently bonded to the T and bonded with varying degrees of covalency and coordination to the metal atom, and, optional Rn substituents are selected from the group consisting of at least one saturated substituent covalently bonded to the Y, and at least one unsaturated substituent covalently bonded to the Y; (b) preparing a first chemical entity featuring the particular form of the amine bis(phenolate) pre-catalyst of step (a); (c) providing a co-catalyst suitable for activating the particular form of the amine bis(phenolate) pre-catalyst; (d) preparing a second chemical entity featuring the provided co-catalyst of step (c); (e) forming a living catalytic polymerization reaction by mixing (i) the first chemical entity featuring the particular form of the amine bis(phenolate) pre-catalyst, with (ii) the second chemical entity of the provided co-catalyst, with (iii) the alpha-olefin monomer to be catalytically polymerized, whereby the co-catalyst activates the pre-catalyst, whereby combination of the pre-catalyst and the co-catalyst becomes a catalyst for effecting the living catalytic polymerization of the alpha-olefin monomer and for producing at least one poly(alpha-olefin) product; (f) allowing the living catalytic polymerization reaction to progress; (g) terminating the living catalytic polymerization reaction; and (h) isolating the at least one poly(alpha-olefin) product formed by the living catalytic polymerization reaction.
The amine bis(phenolate) ligand-metal chelate pre-catalyst of the present invention, when activated by a co-catalyst under mild reaction conditions, is exceptionally reactive for polymerization of a variety of alpha-olefin monomers, including long chain alpha-olefin monomers such as 1-hexene or 1-octene, for forming a variety of poly(alpha-olefin) products such as poly(1-hexene) or poly(1-octene), having high molecular weight and low molecular weight distribution. The amine bis(phenolate) ligand-metal chelate pre-catalyst is relatively stable under commercially applicable conditions for polymerization of alpha-olefin monomers. Moreover, the pre-catalyst, and related forms of the pre-catalyst, of the present invention are relatively simple to synthesize, primarily due to simple syntheses of the corresponding amine bis(2-hydroxyarylmethyl) ligand precursors from a variety of commercially available inexpensive starting materials, compared to syntheses of metallocene type pre-catalysts.
Several additional particular novelties and advantages provided by the method of the present invention for polymerization of alpha-olefin monomers, are briefly listed herein:
(a) The described method is implemented for providing living polymerization performed under the very rare conditions of room temperature (25xc2x0 C.), characterized by a very narrow polydispersity index (PDI) of close to 1.0.
(b) The described method is implemented by appropriately activating the disclosed non-metallocene pre-catalyst, for forming a catalyst which remains xe2x80x98alivexe2x80x99 for an exceptionally long period of time, of as long as 31 hours, whereby, there is producing xe2x80x98in a living fashionxe2x80x99 a polymer having exceptionally high molecular weight of as high as 450,000 grams/mole.
(c) The described method is implemented for providing living polymerization of alpha-olefin monomers xe2x80x98abovexe2x80x99 room temperature, by using a particular pre-catalyst from the disclosed non-metallocene pre-catalyst family.
(d) The described method, using the disclosed pre-catalyst applicable for living polymerization, is implemented for achieving block co-polymerization of alpha-olefin monomers conducted at room temperature. After employing one monomer, which is either totally or nearly totally consumed in a living fashion, a second monomer is added, yielding a block co-polymer.
(e) The described method is implemented for the polymerization of a variety of monomers, such as 1-hexene, 1-octene, 1,5-hexadiene, and the ones of highest industrial significance: propylene and ethylene.
(f) The described method is implemented for producing polymers having a wide range of molecular weights. In particular, there is producing polymers having molecular weights of as high as 450,000 grams/mole, as well as oligomers with molecular weights of 1000 grams/mole.
(g) The described method is implemented for providing a variety of reactivities, by varying the amine bis(phenolate) ligand and the metal, with varying degrees of exotherm, which contributes to controlling reaction temperature.
(h) The described method is implemented for synthesizing hyper-branched polymers, through production of high olefin oligomers having terminal olefinic groups, and their further polymerization.